What DirectX 11 is, and What It Means to You

Ambient Occlusion

Achieving great realism through light and shadows

It’s all about light. Without light, you can’t see. In 3D games, all lighting is created using mathematical cheats—approximations of how real-world lighting behaves. Some of the most interesting lighting effects lie in the absence of light: darkness and shadows.

Shadows have evolved from simplistic shadow maps—where the shadows all looked the same from any angle—to the more sophisticated techniques used in today’s games.

Variations on ambient occlusion are becoming increasingly more popular. Ambient occlusion takes into account how light falls on objects to create shadows, and that the properties of light and shadows change over distance. Crysis was one of the first games to attempt a form of ambient occlusion, known as screen space ambient occlusion (SSAO). SSAO techniques try to determine where a point in the scene exists relative to other points, and the effect that light falling onto that point has on other parts of the scene. Objects have reflective properties, and may in turn bounce light to other parts of the scene—even those blocked from the direct light source.

Real-world objects tend to have crevices, wrinkles, and depressions, which may not be directly lit by a light source (the sun, for example). But they aren’t dark, either—they pick up light being bounced off other parts of the environment or even a nearby surface of the same object that is in direct light. Previous games often ignored this, so crevices and depressions were either completely dark or looked as brightly lit as the other parts of the object.

Other types of ambient occlusion found in newer games include high-definition ambient occlusion (HDAO) and horizon-based ambient occlusion (HBAO). These are still variations on the same idea—that where a pixel exists relative to other pixels determines how light falls on it, how it bounces that light, and what type of light it is (direct or reflected.)

Above is an HDAO sample from the DirectX SDK. Note the internal shadowing made possible in the lower screen by using this ambient occlusion technique. It is relatively subtle, but the overall scene seems more realistic when you’re running the application in full-screen mode. In the top shot, HDAO is disabled; the bottom one has HDAO enabled.

With DirectX 11, a new technique is emerging called contact hardening. If you think about how real-world shadows behave, you’ll realize that a shadow doesn’t look the same along its full length. Close to the object—say, at the base of a lamp post or tree—the line between shadow and light is sharply delineated (the “hard” in contact hardening.) The farther away from the object, the shadow is more diffuse. That’s because farther away, light seeps into the shadow area from the surrounding environment. Contact hardening shadows using Direct 11 graphics emulate this look. Right now, the only game using contact hardening shadows is STALKER: Call of Pripyat (below).

In this DirectX 11 SDK sample, shadows have harder edges near the object and softer edges farther away, as in real life.

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Aparently you missed the point of this entire article. This was not a comparison of ATI vs Nvidia. This was a comparison of DX11 vs DX10. Yes, ati and nvidia were differentiated in the article because each companies cards respond differently to the added effects.

As far as driver stability goes, neither company has a clean track record for their drivers. Of course an Nvidia fan boy is going to claim he has never had a problem with Nvidia drivers. An ATI fan boy is going to do the same. Having owned my fair share of cards from both manufacturers, I can tell you that they both put out their fair share of lemons. But if you insist that Nvidias shit still smells like roses, I will remind you of their recent driver recall.

Generally speaking, I've had a lot of good experience with DX10 and only a couple of games (like Crysis) actually showed a noticeable decrease in performance over DX9. With everything else, it was either a minor boost or no change at all.

But, the one game that I have to tout is Flight Simulator X, which now runs like a scalded cat in DX10 mode and Windows 7 on a Core i7 920. I was able to increase the detail settings much much further than I could with DX9 and I'm getting more than double the frame rates! With DX9, I'm talking about low end detail settings and barely... I mean BARELY 20 fps. It was a joke, at best. With DX10... I now have plenty of the good detail settings (scenery nearly maxed, textures maxed, further view distances... you name it, all bumped UP) and I get 50+ fps consistently! It's like a whole new simulator! DX10 and FSX FTW!

something that has confused me plenty. lets see i have to think about this, to get a nice DOF, i decrease the shutter and increase the apeture (lets more light in), to get a shot in full focus, i increase the shutter and decrease the aperture(less light in)... yep, you right, i think?

When you increase aperture you allow more light in, but you also allow light coming in from more directions, which will decrease your DOE. Back in highschool VisCom you usually make pinhole cameras, they don't need a lens because the aperture is so small, but the exposure has to be pretty high. It's always a nasty tradeoff. It would be cool to see if you show a reduced DOE for humans in the dark. Maybe it's harder to focus on stuff in the dark because the focus has to be much more accurate, like seeing your blurry clock (outside of fuzzy eyes).

So is it time to buy a DirectX 11 card? I've been weighting this issue for a couple weeks now. I have a 4890 but being a hardware junkie I'm usually in the market to upgrade some part/s of my PC. Would you suggest I go ahead or wait for the next generation of gpus? I want a 5870 but don't want to spend that much.

It's interesting to see the results from Call of Pripyat, which have the GTX 480 being outperformed by a significant margin by the 5870. Can anyone shed some light on why it doesn't perform very well in Call of Pripyat?

I cannot offer direct side by side comparisons, nVidia vs ATI, but there appears to be a lot of traffic in various forums to call into question the lack of stability in ATI's drivers for their video cards. On the other hand, nVidia has provided rock solid drivers for each of their video cards I have owned over the years.

It is relatively easy to compare performance of each company's video cards by using hard numbers for frame rates, and it is not so easy to quantify driver stability, but word of mouth is not so good for ATI, so I'll stick with nVidia.

Aparently you missed the point of this entire article. This was not a comparison of ATI vs Nvidia. This was a comparison of DX11 vs DX10. Yes, ati and nvidia were differentiated in the article because each companies cards respond differently to the added effects.

As far as driver stability goes, neither company has a clean track record for their drivers. Of course an Nvidia fan boy is going to claim he has never had a problem with Nvidia drivers. An ATI fan boy is going to do the same. Having owned my fair share of cards from both manufacturers, I can tell you that they both put out their fair share of lemons. But if you insist that Nvidias shit still smells like roses, I will remind you of their recent driver recall.

I love Nvidia and would pretty much call myself a fanboy, but I will also admit any flaws within their products as well. The ONLY issue I have encountered was the one driver that disabled overclocking... which only lasted a few weeks. All I have had is Nvidia and can't really compare the two brands. I've always had Nvidia and have never run into a problem besides that one driver...which didnt affect me because I dont overclock my cards unless im benchmarking. Theyve treated me well and I know ATI makes good things too. Which is why I don't put them down. But... in the end I am a firm believer that Nvidia is overall a better product because of their technology and software in daily use. ATI is greats stuff, but I think Nvidia will reign supreme. It's like comparing Windows to Linux. Theyre both good, but one is more used than the other for a reason.

This is my opinion and I'm entitled to it....as are you. not trying to start a flame war. We're all here for the same reason, so let's be adults. MaxPC to all!

Everyone is entitled to their opinions. That doesn't make them right. Just kidding :P No, I agree with you. There is nothing wrong with brand loyalty. There are definately products out there that I have a preference for. What annoys me is when people let their love for a logo blind them to any and all flaws in a product. Its blind love for a brand that has made apple so powerful as of late. They could put out a dog turd with an apple logo and people would eat it up.

I think this is a good article and I didn't want to see the comments get derailed into an Nvidia vs ATI dispute. They have both put out good solid drivers, and at times they have put out some barely functional steaming piles of poo.